The embodiments described herein relate generally to arc flash detection and mitigation and, more particularly, to arc flash detection systems for use in reducing nuisance detections.
At least some known electric distribution circuits and switchgear generally have conductors that are separated by insulation, such as air, or gas or solid dielectrics. However, if the conductors are positioned too closely together, or if a voltage between the conductors exceeds the insulative properties of the insulation between the conductors, an arc can occur. For example, the insulation between the conductors can become ionized, which makes the insulation conductive and enables formation of an arc flash.
An arc flash includes a rapid release of energy due to a fault between two phase conductors, between a phase conductor and a neutral conductor, or between a phase conductor and a ground point. Arc flash temperatures can reach or exceed 20,000° C., which can vaporize the conductors and adjacent equipment. Moreover, an arc flash can release significant energy in the form of heat, intense light, pressure waves, and/or sound waves, sufficient to damage the conductors and adjacent equipment. However, the current level of a fault that generates an arc flash is generally less than the current level of a short circuit, such that a circuit breaker may not trip or may exhibit a delayed trip unless the circuit breaker is specifically designed to handle an arc fault condition.
Light sensors may be used to detect the presence of light emitted during an arc flash. However, such sensors are often sensitive to low light levels such that they also detect non-arc-flash light and trigger a “nuisance trip” of a circuit protection device. For example, a typical arc flash event can product light in with luminous flux on the order of 100,000 lux at a distance of three to four feet from the arc flash event, while known light sensors generally saturate at 700 lux or less. Light emitted by a circuit breaker during a trip, by space lighting, or by direct sunlight may cause the light sensor to falsely detect an arc flash event. Thus, there is a need for an arc flash detection system that reliably detects arc flash events and mitigates nuisance trips of circuit protection devices.